Thanks for the information. I bought a proper chest mounted heart rate monitor, and emailed my GP a screenshot showing him the instant rise in blood pressure, and he phoned me the next day, arranged bloods and a cardiologist referral, and I am going to have an ECG next week to check nothing else is going on.
I am lucky insomuch as my GP accidentally chemically castrated me and doesn't want me to sue him so he is being extra helpful.
Once again thank you for your support.